Heard this from a ford mechanic and a couple other mechanics and I have also tried it. With a warm engine (not hot) spray entire engine area with 409 cleaner (be very genreous). Let stand for two minutes (no scrubbing needed) and rinse with a garden sprayer on a wider spray pattern (no straight stream). Pay attention not to soak the alternator or fuse box. All other electrical areas are ok since they are all sealed and waterproofed. I did this on my 09' F 150 and it worked excellent, much. ,much better than i expected. Simple green works just as well. All three guys clean the vehicles they work on this way and have never had any issues. It looks almost showroom clean. If there are any dirty spots left just repeat the process. Wish I took before and after pics.